AKT1 and AKT2 are human homologues of the viral oncogene v-akt.. I previously demonstrated that AKT1 is the true human counterpart of v- akt and that AKT2 encodes a novel related protein serine-threonine kinase. Recently, AKT1 was identified to be activated by various growth factors through PI 3-kinase; whereas AKT2 kinase activation has been examined only with respect to PDGF. The activation of AKT2 by PDGF, however, was significantly lower than that of AKT 1. Alterations of AKT2 have been identified in a significant numbers of human ovarian, pancreatic, lung, and breast carcinomas. I recently demonstrated that overexpression of AKT2 can transform NIH 3T3 cells, whereas AKT1 has not been shown to be oncogenic. In addition, I have also demonstrated that AKT2 is up-regulated in mitotic and actively dividing cells. These data suggest that the signal transduction pathways of AKT2 and AKT1 may differ and that AKT2 may play a significant role in human malignancy. Therefore, I propose to elucidate the normal cellular functions of AKT2 and thus to better understand AKT2 in human oncogenesis. First, I will examine a large series of breast, lung, and pancreatic carcinomas to determine the clinicopathological significance of AKT2 alterations. Second, in vitro and in vivo models of tumorigenesis, using cell lines and transgenic mice respectively, will be employed to define the role of AKT2 in breast cancer development. Third, the AKT2 signaling pathway will be examined through its activity and phosphorylation in addition to identification of its interacting proteins by yeast two-hybrid system. Finally, I Bill examine synthetic and turnover rates of AKT2 at different stages of the cell cycle, especially G2 and M phases, and also the ability of antisense AKT2 in modulation of the malignant phenotype in breast and ovarian cancer cells to generalize my previous observation in pancreatic cancer. The proposed investigations will provide very important information about the role of AKT2 in cell cycle control and malignant transformation as well as the possible target for cancer therapy.